I have exact the same problem trying to connect to a Windows PC from my Mac. I’ve used NoMachine for at least 6 months and it has always worked. from Terminal I get: nc -v 172.17.0.130 4000
Connection to 172.17.0.130 port 4000 [tcp/terabase] succeeded!
I have upgraded MacOS to Sequoia 15.0 since I last used NoMachine. I’ve looked in firewall settings but I cannot see that I need to change anything.
Launching from Terminal works????
Thanks